1. Field of Invention
The present invention relates to a crank pulley decoupling device, and more particularly, to a crank pulley decoupling device capable of utilizing space in the crank pulley and reducing impact between springs.
2. Description of Related Art
In general, a crank is connected to an engine crank shaft by a crank pulley and is driven by a rotational force from an engine transmitted by a belt. The belt transmits the force by friction between the belt and the belt pulley. The types of belt include a flat belt having a flat contact surface and a V belt having a V-shaped contact surface to increase friction coefficient and improve transmission efficiency.
Incidentally, a crank pulley is located under the center of an engine, a water pump pulley is located above the crank pulley, an alternator pulley and an air pump pulley are located upper left and lower left sides of the water pump pulley, respectively, and an air conditioner pump pulley and a power steering pump pulley are located upper right and lower right sides of the water pump pulley. All of the pulleys are designed to receive a rotational force from the crank pulley by one belt.
The crank pulley is fitted into and fixed to the crankshaft together with a timing belt sprocket.
The devices that receive a driving force from the crank pulley of the engine as it is driven, such as an alternator, an air conditioner compressor, and a water pump are collectively referred to as a serpentine belt system. In this system, the crank pulley has an instantaneous speed change due to the intake, compression, power and exhaust strokes in an internal combustion engine with a piston.
To overcome this problem, a crank pulley decoupling device to reduce a tension of the serpentine belt system by reducing an instantaneous speed change of the crank pulley is being developed.
Since a typical crank pulley decoupling device uses one spring, it is difficult to cope with an instantaneous speed change in all of the area while an engine is operating. Accordingly, a two-stage crank pulley decoupling device has been developed, which uses two springs, as shown in FIG. 1.
The two-stage crank pulley decoupling device shown in FIG. 1, however, has the structure in which a first arc spring 11 having a larger diameter includes a second arc spring 12 having a smaller diameter and being long, so that it is limited to design and change the second arc spring 12 due to the space of the crank pulley when an engine starts. Further, friction occurs between springs and thus efficiency and durability are deteriorated.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.